JPH07233000A - Magneto-optical element and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the element which can be used as a Faraday element and has a uniform composition and also high optical quality. CONSTITUTION:The composition of this element is represented by the formula (Cd1-x-yMnxHgy)1Te1 wherein: 0<x<1; 0<y<1. The element consists of a single crystal which has a composition within the range enclosed by the four points, i.e., Mn0.5Hg0.5Te (point (a)), Mn0.6Hg0.4Te (point (b)), Cd0.83Mn0.13Hg0.04Te (point (c)) and Cd0.8Mn0.05Hg0.12Te (point (d)), in the MnTe-HgTe-CdTe pseudo-ternary system phase diagram, and also has a >=300mum thickness and contains substantially no twin or compositional segregation, so that the element can be used in the wavelength regions in the vicinity of each of 0.98, 1.017, 1.047 and 1.064mum bands.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a Faraday rotator in an optical passive element, and the wavelength range of transmitted light is substantially 0.98 μm, 1.017 μm, 1.047 μm, 1.
The present invention relates to a magneto-optical element in the 064 μm band, and particularly to a magneto-optical element suitable for use in an optical isolator used near an excitation light source for an optical amplifier (for example, a laser diode) and an optical magnetic field sensor used in the same wavelength region. . The present invention also relates to a method for manufacturing the magneto-optical element.

[0002]

2. Description of the Related Art In recent years, in an optical communication system, use of an optical fiber amplifier has been studied, which directly amplifies an optical signal as it is without replacing the optical signal with an electric signal. In this case, an Er (erbium) -doped optical fiber is used in the amplifier, and the signal light to be amplified and the pumping light are transmitted through the Er-doped optical fiber to obtain amplified light. When a signal light of 1.55 μm, which is a general wavelength in an optical communication system, is used, the wavelength of the pumping light is 1.4
It has been confirmed that particularly good results are obtained in the case of 8 μm or 0.98 μm.

Of these, the optical fiber amplifier pumped in the 1.48 μm band is not necessarily superior in the obtained optical characteristics to the optical fiber amplifier pumped in the 0.98 μm band, but is 1.48 μm band. Since a reliable pumping laser light source has already been obtained, and an optical isolator corresponding to the 1.48 μm band has already been developed, it has already been put to practical use.

On the other hand, it has been experimentally confirmed that the optical fiber amplifier pumped in the 0.98 μm band has higher efficiency and lower noise characteristics than the optical fiber amplifier pumped in the 1.48 μm band. A suitable high-power laser light source for excitation and an optical isolator in the 0.98 μm band have not existed in the past, which has been a bottleneck in development.

By the way, in an optical fiber amplifier for the 1.48 μm band, it is general to use an element using a magnetic garnet film for a Faraday rotator for an optical isolator, but this element has an insertion loss in the 0.98 μm band. Is too large to be practical. On the other hand, in the 0.98 μm band, a semiconductor laser has recently been developed as a pumping laser light source, and therefore, an optical fiber amplifier using the 0.98 μm band is drawing attention. For these reasons, there is an increasing demand for a small size and low loss optical isolator for the 0.98 μm band, and the development of a Faraday rotator used therefor is required. Further, a laser diode pumped Nd that is about to be used as a pumping light source (1.017 μm and 1.047 μm) of a Pr-doped optical fiber amplifier for 1.3 μm signal light, which has a great possibility of practical use in the future, and a light source for transmission of an optical CATV. : YAG
There is a demand for a compact and low-loss optical isolator for a laser light source (1.064 μm).

0.98 μm, 1.017 μm, 1.04
MnTe-H as a material having low loss and high Faraday rotation coefficient in the vicinity of each band of 7 μm and 1.064 μm
The suitability of the ternary semi-magnetic semiconductor material of gTe-CdTe is disclosed in JP-A-61-123814 (that is, 123
814/1986). Further, regarding the composition region in which the Faraday rotation coefficient is high in the ternary material, the above-mentioned JP-A-61-12 is also used.
3814 and JP-A-3-229217 (that is, 2
29217/1991) and 1993 (19
Japanese Patent Application No. 5-9984 filed on Jan. 25, 1993 (Japanese Patent Application Laid-Open No. 6-1994 published on Aug. 12, 1994)
Proposal has been made by, for example, Japanese Patent No. 222309 (see No. 222230/1994).

[0007]

However, the CdMnHgTe crystals disclosed in these publications are all manufactured by the MBE (Molecular Beam Epitaxy) method or the conventional Bridgman method. It is hard to say that this is a method capable of industrially mass-producing crystalline materials.

Since the MBE method is a method in which the constituent elements of the raw material are vapor-deposited on a base material in a vacuum, the produced crystals are usually extremely thin, of the order of several μm to several tens of μm, and are generally exposed to light. It is difficult to manufacture an element having a size and shape sufficient to obtain the Faraday rotation angle of 45 ° required for the isolator, and at least a thickness of about 300 μm.
In addition, usually, in this method, the prepared crystal is often a different crystal film, and it is difficult to obtain a single crystal element material having excellent optical uniformity used for a Faraday element.

On the other hand, according to the conventional Bridgman method, it is possible to fabricate a device having a sufficient size, but twin crystals are generated during the fabrication, or the composition thereof is changed during the crystal growth. Since a variation called crystal segregation occurs, usually only element materials having a non-uniform composition and low optical quality can be obtained, which causes a decrease in yield and deterioration of optical quality and characteristics. It is not a practical method. Using this conventional Bridgman method, Cd
The case of producing an MnHgTe crystal (single crystal) will be described in detail below.

Using this conventional Bridgman method, CdM
When producing an nHgTe crystal (single crystal), as will be described in detail later, the starting raw material is melted at a melting point equal to or higher than the phase transformation point, and the melted raw material is gradually cooled. Therefore, it always passes through the phase transformation point, and twinning occurs at that time. Further, in this case, the composition of the crystal and the melt changes with the growth of the crystal due to the non-congruent melting, and the composition of the obtained crystal varies depending on the location, so that a crystal having a uniform composition is obtained. Absent.

When twins are present, the optical quality in the vicinity of the boundary is low, and therefore, in order to satisfy the practical optical characteristics as a Faraday rotator, a specific orientation (generally, a direction with respect to the twin planes) is required. It is necessary to cut out the grown crystal in a direction perpendicular to the twin plane), and in these elements, incident light transmits through the twin plane, so that the optical quality is low and the optical characteristics vary widely. Furthermore, the crystals obtained by this production method have a large composition segregation (change in crystal composition), and the values of Verde constant and insertion loss fluctuate greatly in the crystal growth direction. Therefore, a suitable composition range that can be used as a Faraday rotator is obtained. The region of was a very limited part of the manufactured crystal. Since these were inevitable in the crystal by the conventional Bridgman method, a CdMnHgTe crystal in which twinning did not occur and composition segregation was small was demanded.

Next, MnTe-disclosed in the above-mentioned publication.
The optical characteristics of the HgTe-CdTe ternary semi-magnetic semiconductor material will be described. MnTe for obtaining high optical characteristics
As the composition of the ternary semi-magnetic semiconductor material of -HgTe-CdTe, the composition range shown in each of the above-mentioned publications is not necessarily appropriate. Generally, the optical characteristics required for a Faraday element are (1) a large Verdet constant (Faraday rotation angle per unit length / unit applied magnetic field) with respect to the wavelength of transmitted light, and (2) small insertion loss of transmitted light. There are two points. However, the insertion loss is 0.7-
There is a region called a cut-on wavelength where the insertion loss sharply increases in the region of 0.9 μm, and the insertion loss is too large in the vicinity thereof and in the region on the shorter wavelength side, so that it cannot be used as a Faraday rotator. In the case of CdMnHgTe semi-magnetic semiconductor, the value of the cut-on wavelength varies depending on its composition. Therefore, by simply extrapolating the data of optical characteristics outside the target wavelength range, the Faraday rotator can be used in the wavelength range where the device is used. It is impossible to judge whether or not it has sufficient optical characteristics.

Based on this, the above-mentioned JP-A-61-1238
14 and the above-mentioned Japanese Patent Laid-Open No. 3-229217, in the former case, the measured wavelength described in the example is 0.8 μm.
m, 1.3 μm, and 1.5 μm, and the latter is limited to the region of 0.50 to 0.78 μm.

Therefore, in the Faraday rotator designed for use in the 0.98 μm band optical isolator, the composition ranges shown in the above two publications should be applied as they are as a range in which good optical characteristics can be obtained. Is not possible, and it is necessary to newly manufacture CdMnHgTe semimagnetic semiconductors with various compositions and to measure the Verde constant and the cut-on wavelength, which are the optical characteristics, in the required wavelength region in order to know the suitable composition range. .

In the above-mentioned Japanese Patent Application No. 5-9984, the corresponding wavelength range includes the 0.98 μm band, but the wavelength range to be used is fairly wide, 0.8 to 1.1 μm. Therefore, compared to the case where the wavelength used is limited to the vicinity of 0.98 μm, the composition region of the scope of the claims is conversely narrowed, and good optical characteristics can be obtained only in this region. It cannot be said that the composition range of the device is appropriate.

As described above, the Faraday rotator of the CdMnHgTe semi-magnetic semiconductor used in the 0.98 μm band near-wavelength optical isolator is required to be (1) industrially stable and capable of mass production. There is a means.

(2) A composition range of a semi-magnetic semiconductor having a small insertion loss of transmitted light and a sufficiently large Verdet constant in the same wavelength range is presented. The above are two points. However, none of the above-mentioned prior arts have clearly shown this. In the above description, it is premised that the Faraday rotator made of a CdMnHgTe semimagnetic semiconductor is used for the 0.98 μm band near-wavelength optical isolator, but even when it is used as a Faraday rotator for an optical magnetic field sensor that uses transmitted light of the same wavelength. Exactly the same.

Therefore, an object of the present invention is to provide a magneto-optical element having a uniform composition and high optical quality, which can be used as a Faraday element.

Another object of the present invention is to provide a method for producing a magneto-optical element having a uniform composition and high optical quality, which can be used as a Faraday element.

[0020]

According to the present invention, (Cd
_1-XY Mn _x Hg _Y ) ₁ Te ₁ (0 <X <1, 0 <Y <
In the magneto-optical element represented by 1), MnTe-Hg
In the Te-CdTe quasi-ternary phase diagram, Mn _0.5 Hg
_0.5 Te, Mn _0.6 Hg _0.4 Te, Cd _0.83 Mn _0.13
Hg _0.04 Te, Cd _0.83 Mn _0.05 Hg _0.12 Te having a composition contained in a range surrounded by four points and having a thickness of 300 μm
A magneto-optical element having the above-mentioned thickness and made of a single crystal substantially free of twinning and composition segregation is obtained.

Further according to the present invention, (Cd _{1 -XY} Mn _x
A magneto-optical element represented by Hg _Y ) ₁ Te ₁ (0 <X <1, 0 <Y <1), wherein MnTe-HgTe-CdT.
In the pseudo ternary phase diagram of e, Mn _0.5 Hg _0.5 Te,
Mn _0.6 Hg _0.4 Te, Cd _0.83 Mn _0.13 Hg _0.04 T
e, Cd _0.83 Mn _0.05 Hg _0.12 Te, and the magnetic composition comprising a single crystal having a composition contained in a range surrounded by four points and having a thickness of 300 μm or more and substantially not containing twin crystals and composition segregation. In the method for manufacturing an optical element, the ratio of elements other than Te to the target composition contained in the above range in the pseudo ternary phase diagram is kept as it is in Te
Cd, metal Mn, metal Te, and metal HgTe mixed in such a proportion that 0.001 to 0.1 are in excess.
Or a raw material consisting of Cd, Mn, Te, and Hg as a starting raw material; the starting raw material being maintained at a pressure corresponding to the vapor pressure of Hg, and Placing the material in an atmosphere maintained at a temperature at which it can be melted, melting the starting material into a melted material; quenching and solidifying the melted material into a polycrystal; Recrystallizing and growing the single crystal by a solid-state reaction by placing the body in an atmosphere maintained at a pressure corresponding to the vapor pressure of Hg and at a temperature lower than the phase transformation temperature of the polycrystalline body. A method for manufacturing a magneto-optical element, which comprises:

[0022]

EXAMPLES Next, examples of the present invention will be described in detail.

Referring to FIG. 1, a magneto-optical element according to an embodiment of the present invention comprises (Cd _1-XY Mn _x Hg _Y ) ₁ Te.
_{In the} magneto-optical element represented by ₁ (0 <X <1, 0 <Y <1), wavelength regions 0.98 μm, 1.017 μm,
Pseudo 3 of MnTe-HgTe-CdTe so that it can be used in the vicinity of each wavelength of 1.047 μm and 1.064 μm band.
In the original phase diagram, Mn _0.5 Hg _0.5 Te, Mn _0.6
Hg _0.4 Te, Cd _0.83 Mn _0.13 Hg _0.04 Te, Cd
_0.83 Mn _0.05 Hg _0.12 Te Single crystal having a composition contained in a range surrounded by four points a, b, c, and d, and having a thickness of 300 μm or more and substantially free of twinning and composition segregation. Consists of.

As will be described in detail later, the magneto-optical element made of the above-mentioned single crystal is simply manufactured as follows. That is, in the quasi-ternary phase diagram, the ratio of elements other than Te was kept as it is with respect to the target composition contained in the above range, and Te was blended in a ratio of 0.001 to 0.1 in excess. Raw material (or metal Cd, metal Mn, metal Mn, metal Te, and metal HgTe)
A raw material composed of metal Te and metal Hg) is prepared as a starting material, and the starting material is filled in a quartz crucible. The inside of the quartz crucible filled with the starting material is set to a pressure corresponding to the vapor pressure of Hg, and the quartz crucible filled with the starting material is installed in a uniform heating region of the heating furnace to melt the starting material. Then, the melted raw material is rapidly cooled and solidified to form a polycrystalline body. Next, place the quartz crucible containing this polycrystal in
The quartz crucible containing the polycrystal is moved to a region having a specific temperature gradient (described later) of the heating furnace, and is maintained at a temperature lower than the phase transformation temperature of the polycrystal, and corresponds to the vapor pressure of Hg. The single crystal is recrystallized by a solid phase reaction by leaving it in an atmosphere maintained at a pressure for several days.

In this manufacturing method, a rod of polycrystalline raw material having a composition substantially corresponding to a target composition manufactured by the quench method (high pressure melting and cooling method) is vacuum-sealed in an ampoule-shaped crucible, and this crucible is heated. By maintaining the temperature below the phase transformation point of the polycrystalline raw material for several days, a single crystal is produced by recrystallizing and growing the polycrystalline raw material. According to this manufacturing method, the above-mentioned drawbacks of the conventional Bridgman method are solved, twin crystals are not generated, and high-quality single crystals with extremely small composition segregation can be mass-produced.

By including the above-mentioned magneto-optical element made of a single crystal as a Faraday rotator, it has substantially high characteristics of isolation: 30 dB or more and insertion loss: 0.5 dB or less, and is small in size in an LD module. 0.98μm, 1.017μ, 1.047μm, which can be mounted
An optical isolator for each near wavelength band of 1.064 μm can be obtained. Similarly, it is also possible to obtain a high-performance magneto-optical sensor using the transmitted light in the above wavelength band by providing the above-mentioned magneto-optical element made of a single crystal as a Faraday rotator.

It is known that Cd _1-x Mn _x Te (0 <X <1) in which a part of Cd of CdTe having a ZnS type structure is replaced with Mn is an element having a large Verdet constant. It is known to be used as a Faraday rotator for an optical isolator in a transmitted light region of 0.63 to 0.85 μm. However, the element is 0.98 μm, 1.017 μm, and 1.047 μm, which are the target regions in the present invention.
Since the Verdet constant is small at each wavelength in the m and 1.064 μm band, sufficient optical characteristics cannot be obtained as a Faraday rotator. This is generally Cd
The MnTe element has a characteristic that the Verdet constant becomes large near the cut-on wavelength, and this is because the value is 0.6 to 0.7 μm in the element. In order to obtain a sufficiently large Verdet constant in the vicinity of each band using this device, the composition value of Mn is changed to increase the absolute value of the Verdet constant, and at the same time, a part of Cd is replaced with Hg. Then, the cut-on wavelength may be shifted to the 0.9 μm band. However, it cannot be used as a Faraday rotator because the insertion loss of the element increases in the region of the cut-on wavelength itself. From the viewpoint of insertion loss, it is desirable that the cut-on wavelength for using the CdMnHgTe element near each of the above bands is 0.94 μm or less. At this time, the insertion loss at a wavelength of 0.98 μm is 0.5 dB or less (the transmittance is 90% or more),
This value is small enough to be used as a Faraday rotator for an optical isolator. It should be noted that the final optical characteristics of the element are also greatly affected by the crystallinity that influences the optical quality of the bulk element.

On the other hand, also in the method of manufacturing a CdMnHgTe single crystal, the manufacturing method proposed in the present invention can be greatly improved. That is, a rod of polycrystalline raw material having a composition corresponding to the target composition, which is produced by the quench method (high-pressure melting and cooling method), is vacuum-enclosed in an ampoule-shaped crucible, and this crucible heating device lowers the phase transformation point of the crystal of the target composition. By maintaining the temperature, the polycrystalline raw material is recrystallized and grown to produce a single crystal. At that time, in order to prevent problems in crystal growth (pressure strain in the quartz crucible, precipitation of Hg, etc.), the pressure, temperature, and temperature gradient should be set to appropriate values at all times, and repeated in the same equipment. It is possible to manufacture a device crystal having a stable composition. By taking the above method, in principle, the generation of twins, which was a major problem for the optical quality in the conventional Bridgman method, is eliminated in principle, and the composition segregation that causes a great variation in the optical characteristics of the crystal is eliminated. Since the Faraday rotator element crystal having high optical characteristics can be manufactured with a high yield because it can be suppressed to a range where practically no problem occurs, it is possible to mass-produce industrially by this method for the first time.

Next, specific examples of the present invention will be described.

Here, C corresponding to the composition at point c in FIG.
In the case of producing a single crystal of d _0.83 Mn _0.13 Hg _0.04 Te, both the conventional Bridgman method and the manufacturing method according to the present invention will be described below.

FIG. 2 shows a schematic structure of a manufacturing apparatus for executing the conventional Bridgman method. Target ratio of metal Cd, metal Mn, metal HgTe, and metal Te (molar number ratio; Cd: Mn: HgTe: Te = 0.83:
0.13: 0.04: 0.96) as a starting material, and then the starting material is loaded into a quartz crucible 3 and the pressure vessel 8 is vacuum-sealed in the presence of an argon gas 9.
After melting in the melting zone H of the electric furnace 1 of the high-pressure Bridgman furnace (conditions: melting point of about 1050 ° C., pressure of about 20 atm) to form a melt 4, the quartz crucible 3 is set to 3 to 7 mm / hour.
At a rate of 5 ° C. and cooled from the lower side thereof to sequentially grow crystals from the lower end side of the quartz crucible 3 to obtain a single crystal 5. Crystals obtained by this method have a melting point (1050
C.) to the phase transformation point (950.degree. C.), a wurtzite structure is formed, and then at a temperature below the phase transformation point, it changes to a sphalerite structure. From the above, when this manufacturing method is adopted, twin crystals are generated in the obtained crystal, and the optical characteristics change in the crystal growth direction due to the composition variation. Therefore, the obtained crystal can be used only as a material for an optical element in a specific plane orientation and a specific region, so that the yield is reduced. Therefore, in this crystal, the region which can be used as a Faraday rotator is a small part of the whole crystal, and the quality is insufficient.

FIG. 3 is an infrared polarization micrograph of the structure of a semimagnetic semiconductor crystal manufactured by the conventional Bridgman method. In FIG. 3, there is a growth start portion on the back side of the photograph, and the crystal grows from there toward the front side of the photograph. A striation-like structure is clearly observed on the entire surface in the oblique direction of this photograph, which is the boundary surface of the generated twin. The distance between the boundary surfaces, that is, the thickness of the uniform single crystal region is about 30 μm in this case.

FIG. 4 shows a schematic structure of a manufacturing apparatus for carrying out the manufacturing method according to the present invention. In the case of producing a single crystal of Cd _0.83 Mn _0.13 Hg _0.04 Te corresponding to the composition at point c in FIG. 1, the high-purity metal metal Cd, metal Mn, metal HgTe, and metal Te are slightly more Te than the target ratio. Excessive weighing (Te excess 0.001 (ie 0.1
%) Or more and 0.1 (that is, 10%) or less, in this example, 0.
01 (ie, 1.0%) excess. Molar ratio; Cd:
Mn: HgTe: Te = 0.83: 0.13: 0.0
4: 1.01) and used as the starting material. Next, the starting material is loaded into the quartz crucible 3 and the pressure vessel 8 is filled with argon gas 9
In a melting zone H of the electric furnace 1 (condition: melting point: about 1050 ° C., pressure: about 20 at)
m) to form a melt, and then rapidly cooled to produce a polycrystalline sintered rod 6. After that, the heating region is subjected to an appropriate temperature gradient (~ 10).
The quartz crucible is moved to a position where the temperature gradient of ° / cm exists in the vertical direction and becomes lower as it goes downward) by using the crucible moving mechanism of the apparatus, and the temperature lower than the phase transformation temperature ( Up to 880 ° C.) at a pressure of about 15 atm and recrystallization is performed to grow the single crystal 5. The temperature during the growth of the single crystal 5 (about 900 ° C.) is the phase transformation point (about 95 ° C.).
Since it is below 0 ° C.), the single crystal 5 has a zinc blende type structure from the beginning. Therefore, in this case, twin crystals do not occur because the phase does not pass through the phase transformation point in the crystal cooling process. Further, the composition segregation of the crystal is extremely small due to the growth below the melting point, and with the crystal having the above composition, a growth body having a single-crystallized region with a yield of 90% or more could be obtained.

FIG. 5 is an infrared polarization micrograph of the structure of the semimagnetic semiconductor crystal manufactured by the manufacturing method of the present invention. In FIG. 5, there is a growth start portion on the back side of the photograph, and crystals grow from there to the front side of the photograph. Unlike the case of manufacturing by the conventional Bridgman method shown in FIG. 3,
No vertical streak structure due to twinning was observed, indicating a uniform optical quality.

Referring to FIG. 6, the Hg concentration distribution a in the length direction of the crystal grown by the above-described manufacturing method of the present invention.
And the Hg concentration distribution b in the length direction of the crystal grown by the above-mentioned conventional Bridgman method. In addition, c indicates the target composition of the crystal. Also, the Hg concentration on the vertical axis in this figure is the composition formula of the crystal Cd _{1 -XY} M
It corresponds to the value of Y represented by n _x Hg _Y Te (0 <X <1, 0 <Y <1).

Using the above-described manufacturing method of the present invention, single crystals of CdMnHgTe having various compositions in the pseudo-ternary phase diagram of MnTe-HgTe-CdTe were prepared, and their Verdet constant and insertion loss were measured. , The composition range suitable for the Faraday rotator was examined. FIG. 7 shows the position of the composition where the crystal was actually manufactured and the optical characteristics were measured and the value of the Verdet constant at that composition. The measurement position is a total of 30 points shown in the figure.

In general, in the case of a CdMnHgTe single crystal, the value of the Verdet constant of the Faraday rotator is required to be 0.03 deg / cm · Oe or more at the operating wavelength due to the operating conditions. This is because if a permanent magnet with a magnetic field strength of 3000 Oe is used, the total length of the Faraday rotator that rotates the polarization plane of the transmitted light by 45 ° is 5 mm. Using a permanent magnet with a magnetic field strength of more than 3000 Oe or C
This is because a design in which the total length of the dMnHgTe single crystal exceeds 5 mm is not realistic. Then, when the region where the value of Verde constant is 0.03 deg / cm · Oe or more is shown in FIG. 2, it is on the circumference of the quadrangle connecting the four points a, b, c, d shown by the dotted line in the figure, and inside thereof, This is 4 points a in Fig. 1,
This corresponds to the composition range surrounded by b, c and d. It is important for the optical characteristics of the Faraday rotator to have a large Verdet constant and a small insertion loss, but at the points inside the quadrangle in the figure, the cut-on wavelength is 940 nm or less, and when used as an isolator. It has been confirmed that the insertion loss of is less than 0.5 dB.

Next, using a CdMnHgTe single crystal within the composition range surrounded by four points a, b, c and d in FIG.
An example of manufacturing an optical isolator for the μm band will be shown below. Cd _0.83 Mn having a composition corresponding to point c in FIGS. 1 and 2
_{A 0.13} Hg _0.04 Te single crystal was manufactured by the manufacturing method according to the present invention described above, and was used as a Faraday rotator, and the magnetic field strength was 300.
An optical isolator having a structure in which a magnetic field was applied by inserting it into the 0 Oe Nd-Fe-B cylindrical permanent magnet was manufactured. The shape of the Faraday rotator is 1.7 mm x 1.7 mm x 5 mm
The surface of the light transmission region is coated with a non-reflection coating for 0.98 μm. As the polarizing element, two glass polarizers similarly coated with antireflection coating were used. The size of the optical isolator is as small as φ8 mm × 8 Lmm. The optical characteristics are isolation: 30 dB, insertion loss:
0.5 dB, both of which are 0.
It is a value that can be used perfectly as an optical isolator for the 98 μm band.

On the other hand, in the case of using the crystal manufactured by the conventional Bridgman method, the characteristics of the optical isolator for the 0.98 μm band having the same structure is 25 dB and the insertion loss is 1 even if the best crystal part is used. It was 0.0 dB, which was extremely insufficient for practical use.

[0040]

As described above, according to the present invention,
Cd _1-XY Mn _x Hg _Y Te (0 <X <1, 0 <Y, which is suitable as a magneto-optical element for an optical isolator used for an amplifier excitation light source or the like (0.98 to 1.064 μm)
It is possible to provide a magneto-optical element made of the semi-magnetic semiconductor crystal shown in <1).

Further, according to the present invention, there is provided a method capable of efficiently producing the above semi-magnetic semiconductor as a high quality single crystal free from twins and having sufficiently small composition segregation.

Further, according to the present invention, by using the magneto-optical element as a Faraday rotator, an excitation light source for an amplifier (0.98 μm band, 1.017 μm band, 1.047 μm band)
A compact and high-performance optical isolator suitable for the band and the 1.064 μm band can be obtained.

Further, according to the present invention, the magneto-optical element is used as a Faraday rotator, and the working wavelength is 0.98 μm.
Band, 1.017 μm band, 1.047 μm band, and 1.0
A high performance optical magnetic field sensor in the 64 μm band can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a composition range of a magneto-optical element according to an example of the present invention in a pseudo-ternary phase diagram of MnTe-HgTe-CdTe.

FIG. 2 is a diagram for explaining the operation of the crystal manufacturing apparatus for performing the conventional Bridgman method.

FIG. 3 is Cd manufactured by the conventional Bridgman method.
It is an infrared polarization micrograph of the structure of the semimagnetic semiconductor crystal which has a composition represented by MnHgTe.

FIG. 4 is a diagram for explaining the operation of the crystal manufacturing apparatus for carrying out the manufacturing method according to the present invention.

FIG. 5: CdMn manufactured by the manufacturing method of the present invention
3 is an infrared polarization micrograph of the structure of a semimagnetic semiconductor crystal having a composition represented by HgTe.

FIG. 6 is a diagram showing a comparison of composition segregation distributions of crystals produced by the conventional Bridgman method and the production method of the present invention.

FIG. 7 is a diagram showing the Verdet constant values for each composition of a semi-magnetic semiconductor single crystal in a pseudo-ternary phase diagram of MnTe-HgTe-CdTe.

[Explanation of symbols]

 1 Electric Furnace 3 Quartz Crucible 4 Melt 5 Single Crystal 6 Sintering Rod 8 Pressure Vessel 9 Argon Gas

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G02F 1/37 // G02B 27/28 A

Claims (8)

[Claims] 1. (Cd _1-XY Mn _x Hg _Y ) ₁ Te
₁ in the magneto-optical element represented by (0 <X <1,0 <Y <1), the pseudo-ternary phase diagram of _{MnTe-HgTe-CdTe, Mn 0.5} Hg 0.5 Te, Mn 0.6 Hg 0.4 Te, Cd
_0.83 Mn _0.13 Hg _0.04 Te, Cd _0.83 Mn _0.05 Hg
_It has a composition contained in the range surrounded by four points of _0.12 Te, and 30
A magneto-optical element comprising a single crystal having a thickness of 0 μm or more and substantially free of twin crystals and composition segregation. 2. The magneto-optical element according to claim 1, which is used in a wavelength region of substantially 0.98 μm band. 3. The magneto-optical element according to claim 1, which is used in a wavelength region of substantially 1.017 μm band. 4. The magneto-optical element according to claim 1, which is used in a wavelength region of substantially 1.047 μm band. 5. The magneto-optical element according to claim 1, which is used in a wavelength region of substantially 1.064 μm band. 6. An optical isolator comprising the magneto-optical element according to claim 1 as a Faraday rotator. 7. An optical magnetic field sensor comprising the magneto-optical element according to claim 1 as a Faraday rotator. 8. (Cd _1-XY Mn _x Hg _Y ) ₁ Te
₁ A magneto-optical element represented by (0 <X <1,0 <Y <1), the pseudo-ternary phase diagram of _{MnTe-HgTe-CdTe, Mn 0.5} Hg 0.5 Te, Mn 0.6 Hg 0.4 Te , Cd
_0.83 Mn _0.13 Hg _0.04 Te, Cd _0.83 Mn _0.05 Hg
_It has a composition contained in the range surrounded by four points of _0.12 Te, and 30
A method of manufacturing the magneto-optical element comprising a twin crystal and a single crystal substantially free of composition segregation having a thickness of 0 μm or more, wherein a target composition included in the range in the pseudo ternary phase diagram is used. , Te, the ratio of elements other than Te remains unchanged, and T
The metal Cd, the metal Mn, the metal Te, and the metal HgT mixed in such a ratio that e is 0.001 or more and 0.1 or less in excess.
a step of preparing a starting material composed of e or a material composed of metal Cd, metal Mn, metal Te, and metal Hg as a starting material; the starting material being maintained at a pressure corresponding to the vapor pressure of Hg, and Placing the raw material in an atmosphere maintained at a temperature capable of melting the raw material to melt the starting raw material into the melted raw material; quenching and solidifying the melted raw material into a polycrystal; The single crystal is recrystallized by solid phase reaction by placing the crystal in an atmosphere maintained at a pressure corresponding to the vapor pressure of Hg and lower than the phase transformation temperature of the polycrystal. And a step of manufacturing the magneto-optical element.